U.S. patent number 7,088,397 [Application Number 09/715,794] was granted by the patent office on 2006-08-08 for image sensor packaging with imaging optics.
This patent grant is currently assigned to Avago Technologies General IP Pte. Ltd. Invention is credited to James-Yu Chang, Andrew Arthur Hunter, Ray Schuder, Park-Kee Yu.
United States Patent |
7,088,397 |
Hunter , et al. |
August 8, 2006 |
Image sensor packaging with imaging optics
Abstract
A digital image capture system includes an image sensor, a
package structure for holding the image sensor, and electrical
connectors for creating electrical connections between the image
sensor and a circuit board. The package structure includes
attachment features that enable an optics system to be securely
attached to the package structure after the package structure has
been soldered to the circuit board In an embodiment, the attachment
features align the optics system with the image sensor without
having to power up the image sensor. An embodiment of the
attachment features includes mechanical attachment features, such
as clip arms and/or clip receivers. In an embodiment, the optics
system includes attachment features that are complementary to the
attachment features of the package structure. The package structure
and optics system may additionally include complementary contact
surfaces that create a light-tight connection between the optics
system and the package structure.
Inventors: |
Hunter; Andrew Arthur (Bristol,
GB), Chang; James-Yu (Cupertino, CA), Yu;
Park-Kee (San Jose, CA), Schuder; Ray (Menlo Park,
CA) |
Assignee: |
Avago Technologies General IP Pte.
Ltd (Singapore, SG)
|
Family
ID: |
36942013 |
Appl.
No.: |
09/715,794 |
Filed: |
November 16, 2000 |
Current U.S.
Class: |
348/374;
348/E5.028; 348/E5.027; 257/433; 250/239 |
Current CPC
Class: |
G02B
7/022 (20130101); H04N 5/2253 (20130101); H04N
5/2254 (20130101) |
Current International
Class: |
H04N
5/225 (20060101) |
Field of
Search: |
;348/335,340,373,374
;257/291,294,433 ;250/216,239 ;24/545,457 ;292/17,80,253 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Vu; Ngoc-Yen
Assistant Examiner: Yoder; Chriss S.
Claims
What is claimed is:
1. A digital image capture system comprising: an image sensor; a
package structure for holding said image sensor, said package
structure including attachment means for attaching an optics system
to said package structure; electrical connectors for creating
electrical connections between said image sensor and a circuit
board; a transparent cover connected to said package structure that
encloses said image sensor within a cavity of the package
structure; and a removable protective barrier, connected to said
attachment means, that protects said transparent cover from
damage.
2. The digital image capture system of claim 1 wherein said
attachment means includes an irregular surface on said package
structure for mechanically attaching said optics system to said
package structure.
3. The digital image capture system of claim 1 wherein said
attachment means includes a recess on said package structure for
mechanically attaching said optics system to said package
structure.
4. The digital image capture system of claim 1 wherein said
attachment means includes a clip receiver integrated with said
package structure for mechanically attaching said optics system to
said package structure.
5. The digital image capture system of claim 1 wherein said
attachment means includes a clip arm integrated with said package
structure for mechanically attaching said optics system to said
package structure.
6. The digital image capture system of claim 1 wherein said package
structure includes a contact surface that is complementary to a
contact surface of said optics system.
7. The digital image capture system of claim 6 wherein said contact
surface of said package structure is formed to create a light-tight
connection with said contact surface of said optics system.
8. The digital image capture system of claim 1 wherein said
attachment means causes said optics system to be aligned with said
package structure and said image sensor when said optics system is
attached to said package structure.
9. The digital image capture system of claim 1 further including an
alignment feature integrated into said package structure for
aligning said optics system with said image sensor.
Description
FIELD OF THE INVENTION
The invention relates generally to digital image capture systems,
and more particularly to the packaging of image sensors in
conjunction with imaging optics.
BACKGROUND OF THE INVENTION
Digital cameras, either still or video, utilize image sensors to
capture digital image information. As with conventional film based
cameras, digital cameras include imaging optics to focus light onto
the image capture medium.
In order to reduce assembly time and cost for high volume digital
cameras, it is important that the number of circuit boards required
to mount all of the components, including the image sensor and
imaging optics, be kept to a minimum and that the components have
as small a footprint as possible. In addition, it is important that
the electronic components can be attached to the circuit boards
utilizing standard automated mounting techniques, such as widely
utilized surface mounting techniques.
It is also important in digital camera applications that the
imaging optics be accurately aligned with the image sensor so that
the image bearing light is focused onto the image sensor. One
technique for accurately aligning the imaging optics with the image
sensor involves powering up the image sensor and adjusting the
location of the imaging optics in response to a detected image.
Powering up the image sensor to align the imaging optics is time
consuming and requires specialized alignment equipment. Other
techniques for accurately aligning the image sensor with the
imaging optics do not involve powering up the image sensor.
Various digital image capture systems having an image sensor and
imaging optics that can be aligned without powering up the imaging
sensor have been adapted for high volume camera production. FIG. 1
depicts a first prior art digital image capture system which has an
image sensor package 102 that is surface mounted to a circuit board
104, with the circuit board being attached to the outer case 106 of
a digital camera. The imaging optics 108 are also connected to the
outer case of the digital camera in a manner which allows image
bearing light to contact an image sensor. The digital image capture
system of FIG. 1 includes the outer case, the printed circuit
board, the image sensor package, an image sensor chip 110, package
leads 112, an image sensor cover glass 114, a lens holder 118, lens
elements 120, a lens aperture 122, and an infra-red filter 124.
Although the arrangement of image capture elements works well,
accurate alignment of the lens elements with the image sensor is
made difficult because of the distance between the lens elements
and the image sensor and because the outer case typically has
slight flexibility that can change the alignment. In addition, the
outer case must be light-tight to ensure that unwanted light does
not reach the image sensor.
FIG. 2 depicts a second prior art digital image capture system in
which an image sensor package 202 is attached to a circuit board
204 and imaging optics 208 are attached directly to the same
circuit board around the outer edges of the image sensor package.
The digital image capture system of FIG. 2 includes the circuit
board, the image sensor package, an image sensor chip 210,
connection leads 212, an image sensor cover glass 214, a light
shield 226, an infra-red filter 224, a filter retaining ring 228, a
lens attachment structure 230, lens attachment screws 232, a lens
holder 218, lens elements 220, and a lens aperture 222. Although
the arrangement of image capture elements works well, the circuit
board must be designed and built with precisely aligned attachment
holes for attaching the imaging optics. Even with precisely aligned
attachment holes for the imaging optics, the image sensor package
must be mounted on the circuit board with precise accuracy in order
to ensure alignment between the imaging optics and the image
sensor. In addition, the attachment structure of the imaging optics
extends beyond the outer edges of the image sensor package, thereby
taking up valuable circuit board real estate.
FIG. 3 depicts a third prior art digital image capture system in
which an alignment plate 334 is utilized to ensure alignment
between an image sensor package 302 and imaging optics 308. The
digital image capture system includes a circuit board 304, the
alignment plate, the image sensor package, an image sensor chip
310, connection leads 312, an image sensor cover glass 314, a light
shield 326, an infra-red filter 324, a filter retaining ring 328, a
lens attachment structure 330, connection nuts 340 and bolts 342, a
lens holder 318, lens elements 320, and a lens aperture 322. The
alignment plate is located between the circuit board and the image
sensor package and the imaging optics. The alignment plate includes
through holes that enable the connection leads of the image sensor
package to connect to the circuit board. The alignment plate also
includes through holes for aligning and attaching the lens
attachment structure to the circuit board. Because the image sensor
package and the lens attachment structure are aligned with the
alignment plate, the image sensor chip and the imaging optics are
indirectly aligned with each other. Although the arrangement of
image capture elements works well to improve the alignment problem
described with reference to the image capture system of FIG. 2, the
alignment plate is not compatible with surface mounting techniques
that are utilized to attach image sensing packages in high volume
assembly processes. In addition, the alignment plate adds extra
cost to the image capture system.
In all of the above-described digital image capture systems, the
image sensor is sealed within a package cavity by a cover glass.
The cover glass protects the image sensor from damage while the
image sensor package is soldered to the circuit board. Other
techniques for attaching and aligning imaging optics with an image
sensor involve attaching the imaging optics directly to a surface
of the image sensor. While this provides some advantages, the
imaging optics must be attached to the image sensor in a clean-room
environment because the image sensor is very sensitive to
environmental contaminants. Because the imaging optics must be
attached to the image sensor in a clean-room environment, the
imaging optics are typically attached to the image sensor before
the image sensor is soldered to a circuit board. In order to
minimize the exposure of the image sensor and the imaging optics to
the high temperatures required for surface mounting techniques,
some image sensor packages and imaging optics are through hole
mounted to the circuit boards and soldered from the back, often by
labor intensive hand soldering.
The description of prior art image capture systems is not meant to
be exhaustive although it does highlight some of the problems
involved with assembling image capture systems, such as high volume
digital cameras, that utilize image sensor chips and imaging
optics. In view of the problems involved with assembling image
capture systems, what is needed is an economic technique for
assembling an image capture system that ensures precise alignment
between the image sensor and the imaging optics without having to
power up the image sensor, without exposing the image sensor to
contaminants, and without exposing the imaging optics to the high
temperatures of the surface mounting process.
SUMMARY OF THE INVENTION
An embodiment of a digital image capture system includes an image
sensor, a package structure for holding the image sensor, and
electrical connectors for creating electrical connections between
the image sensor and a circuit board. The package structure
includes attachment features that enable the optics system to be
securely attached to the package structure after the package
structure has been soldered to the circuit board. The optics system
can be attached directly to the package structure after the surface
mounting process is complete to create a light-tight connection
between the package structure and the optics system. In addition,
the attachment features can align the optics system with the image
sensor without having to power up the image sensor.
An embodiment of the attachment features includes mechanical
attachment features, such as clip arms and/or clip receivers. In an
embodiment, the image sensor is sealed within a cavity of the
package structure by a transparent cover.
The package structure may additionally include a contact surface
that is complementary to a contact surface of the optics system and
alignment features, separate from the attachment features, that
allow the optics system to be aligned with the image sensor.
Another embodiment of a digital image capture system includes an
image sensor package and an optics system connected to the image
sensor package. The image sensor package includes an image sensor,
a package structure for holding the image sensor, and electrical
connectors for creating electrical connection between the image
sensor and a circuit board. The package structure includes
attachment features for attaching the optics system to the image
sensor. The optics system includes a lens and a lens holder
structure for holding the lens. The lens holder structure includes
attachment features for attaching the optics system to the image
sensor.
Another embodiment of a digital image capture system includes a
circuit board, an image sensor package connected to the circuit
board, and an optics system connected to the image sensor package.
The circuit board includes electrical contact points. The image
sensor package includes an image sensor, a package structure for
holding the image sensor, and electrical connectors that are
attached to the electrical contact points of the circuit board to
create electrical connections between the image sensor and the
circuit board. The package structure includes attachment features
for attaching the optics system to the image sensor. The optics
system includes a lens and a lens holder structure for holding the
lens. The lens holder structure includes attachment features for
attaching the optics system to the image sensor.
An advantage of the above described digital image capture systems
is that an image sensor package can be soldered to a circuit board
using conventional surface mounting techniques before the optics
system is attached to the image sensor package. The optics system
can then simply be "clipped" onto the image sensor package into a
position that automatically aligns the optics system with the image
sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an example depiction of a prior art digital image capture
system in which a circuit board and imaging optics are attached to
the outer case of a digital camera.
FIG. 2 is an example depiction of a prior art digital image capture
system in which imaging optics are attached to the same circuit
board as an image sensor package.
FIG. 3 is an example depiction of a prior art digital image capture
system in which an alignment plate is utilized to ensure alignment
between an image sensor package and imaging optics.
FIG. 4A is a depiction of an image capture system in which imaging
optics are directly connected to a surface mounted image sensor
package in accordance with an embodiment of the invention.
FIG. 4B is an expanded depiction of contact surfaces, alignment
features, and attachment features of the package structure and
optics system shown in FIG. 4A.
FIG. 4C is a top view of the package structure of FIG. 4A that
shows the alignment/attachment features.
DETAILED DESCRIPTION
FIG. 4A is a depiction of an image capture system in which imaging
optics are directly connected to a surface mounted image sensor
package. The image capture system includes a circuit board 404, an
image sensor package 416, and an optics system 408. Each of the
elements and respective sub-elements are described in detail
below.
The circuit board 404 includes a conventional circuit board that is
utilized in image capture applications such as hand-held digital
cameras. In an embodiment, electronic components, such as image
sensor packages, are connected to electrical contact points 450 on
the circuit board utilizing known surface mounting techniques. In a
preferred embodiment, the electronic components are attached with
automated soldering processes that subject the circuit board and
components to temperatures that are too high for many plastic
optical lens components.
The image sensor package 416 includes a package structure 402, an
image sensor 410, connection leads 412, and a transparent cover
414. The image sensor, the connection leads, and the transparent
cover include elements that are known in the field of digital image
capture systems. In an embodiment, the transparent cover includes a
protective barrier that protects the transparent cover from damage
during assembly. The protective barrier is removed before the
optics system 408 is attached. As is described below, the
protective barrier may be attached to the package structure via the
same attachment features that are utilized to attach the optics
system to the image sensor package.
The package structure 402 houses the image sensor 410 and supports
the connection leads 412 that electrically connect the image sensor
to the circuit board 404. The package structure prevents unwanted
light from reaching the image sensor and allows image bearing light
to reach the image sensor only through the transparent cover 414.
The package structure may be made of known packaging materials such
as plastic or ceramic.
The package structure 402 is designed to create a connection
between the package structure and the optics system 408 that is
light-tight and that accurately aligns the optics system with the
image sensor 410. In order to create a connection that is
light-tight and that accurately aligns the optics system with the
image sensor the package structure includes a contact surface 452,
or surfaces, and attachment features. The package structure may
also include alignment features that help to accurately align the
optics system with the package structure. As will become apparent,
some portions of the package structure may serve multiple roles,
such as part contact surface(s) and part alignment feature, or part
attachment feature and part attachment feature.
The contact surface 452 of the package structure 402 is a surface
that is formed to create a light-tight connection between the
package structure and the optics system 408. Referring to FIG. 4B,
in an embodiment, the contact surface includes a continuous surface
around the package structure that is complimentary to a contact
surface 458 of the optics system. That is, the contact surface of
the package structure fits directly against an opposite contact
surface of the optics system. In an embodiment, the contact
surface, or surfaces, of the package structure may include seals or
irregularities, such as dark color baffles, that ensure a
light-tight and secure connection between the image sensor package
416 and the optics system. Baffles may be used to ensure that
leaking light is reflected one or more times and a dark color is
used to ensure that light is absorbed and not reflected.
The attachment features are features of the package structure 402
that enable the optics system 408 to be securely attached to the
image sensor package 416. In an embodiment, the attachment features
may include exterior and/or interior features such as clips and/or
clip receivers. As shown in FIGS. 4A 4C, the package structure
includes clip receivers 454 and 456 on the exterior of the package
structure that are formed to fit clip arms 460 of the optics
system. It should be noted that although specific attachment
features are shown in FIGS. 4A 4C, other arrangements of attachment
features may be utilized to attach the optics system to the image
sensor package. In an embodiment, the attachment features of the
package structure may be separate from alignment features. Although
the above-described contact surface helps to create a light-tight
connection between the package structure and the optics system, a
package structure having attachment features and no control surface
is possible.
The alignment features of the package structure are features that
cause the optics system to be accurately aligned with the image
sensor once the optics system is attached to the package structure.
In an embodiment, the alignment features may include mechanical
alignment features and/or optical alignment features. Example
mechanical alignment features include notches, grooves, flat
surfaces, protrusions, etc. that are complementary to mechanical
alignment features of the optics system. Example optical alignment
features may include optically detectable markings or notches that
are optically aligned with complementary features on the optics
system. FIG. 4C is a top view of the package structure of FIG. 4A
in which alignment features 454 of the package structure include
four notches in the package structure that form clip receivers. The
clip receivers are aligned to receive clip arms of the optics
system. The clip receivers and clip arms are integrated into the
package structure and the optics system such that alignment of the
clip receivers and clip arms causes alignment of the imaging optics
with the image sensor. In the embodiment of FIGS. 4A 4C, the
alignment features also serve as the attachment features. That is,
the clip arms and clip receivers cause the optics system to be
attached to the package structure as well as aligned with the
package structure and the image sensor.
The optics system 408 includes a lens holder structure 418, imaging
optics 420, and a lens aperture 422. The imaging optics may include
one or more lenses as is known in the field of digital image
capture. The lens, or lenses, may be made of, for example, plastic
or glass and are shaped to direct and focus the desired image
bearing light onto the image sensor 410. In an embodiment, the
imaging optics and aperture can be adjusted to change parameters
such as the field of view, focus, image magnification, and light
intensity. In an embodiment, the imaging optics include changeable
lens sub-assemblies.
The lens holder structure 418 houses the imaging optics and is
connected directly to the image sensor package. The lens holder
structure may be made of plastic, metal, or some other material or
any combination thereof, as is known in the field of optics
systems.
The lens holder structure 418 is designed to create a connection
between the lens holder structure and the package structure 402
that is light-tight and that accurately aligns the imaging optics
420 with the image sensor 410. In order to create a connection that
is light-tight and that accurately aligns the imaging optics with
the image sensor, the lens holder structure includes the contact
surface 458, or surfaces, and attachment features 460 that are
complementary to the above-described contact surface(s) and
attachment features of the package structure. The lens holder
structure may also include alignment features that help to
accurately align the lens holder structure to the package
structure. Some portions of the lens holder structure may serve
multiple roles, such as part contact surface and part attachment
feature, or part alignment feature and part attachment feature.
The contact surface, or surfaces, 458 of the lens holder structure
418 is a surface that is formed to create a light-tight connection
between the package structure 402 and the optics system 408. In an
embodiment, the contact surface of the lens holder structure
includes a continuous surface around an inner portion of the lens
holder structure that is complimentary to the contact surface 452
of the package structure. That is, the contact surface of the lens
holder structure fits directly against the contact surface of the
package structure. In an embodiment, the contact surface of the
lens holder structure may include seals or irregularities, such as
dark colored baffles, that ensure a light-tight and secure
connection between the image sensor package and the optics
system.
The attachment features of the lens holder structure are features
that enable the optics system 408 to be securely attached to the
image sensor package 416. In an embodiment, the attachment features
may include exterior and/or interior features such as clip arms
and/or clip receivers that are complementary to the attachment
features of the package structure 402. In the embodiment of FIGS.
4A 4C, the lens holder structure 418 includes clip arms 460 on the
exterior of the lens holder structure that are formed to mate with
the clip receivers 456 of the package structure. It should be noted
that although specific attachment features are shown in FIGS. 4A
4C, other arrangements of attachment features may be utilized to
attach the optics system to the image sensor package. For example,
the package structure 402 may have clip arms and the lens holder
may have complementary clip receivers. In an embodiment, the
attachment features of the lens holder structure may be separate
from the alignment features.
In addition to the complementary attachment features of the package
structure 402 and the lens holder structure 418, the optics system
may be more securely attached to the package structure by, for
example, gluing or welding, after the optics system is initially
attached to the package structure by the complementary attachment
features. In an embodiment, the complementary attachment features
of the package structure and lens holder structure serve to hold
the optics system and the package structure together while they are
permanently affixed by gluing or welding. For example, clip arms
and clip receivers may initially attach the optics system to the
package structure while glue is applied and cured, thus ensuring
that the glue does not change the alignment of the optics system to
the image sensor. In an embodiment, the attachment features may be
temporary, or removable, features that are eliminated after the
optics system is permanently affixed to the package structure.
The alignment features of the lens holder structure 418 are
features that cause the optics system 408 to be accurately aligned
with the image sensor 410 once the optics system is attached to the
package structure 402. In an embodiment, the alignment features may
include mechanical alignment features and/or optical alignment
features. Example mechanical alignment features include notches,
grooves, flat surfaces, protrusions, etc. that are complementary to
mechanical alignment features of the package structure. Example
optical alignment features may include optically detectable
markings or notches that are optically aligned with complementary
features on the package structure. In the embodiment of FIGS. 4A
4C, alignment features of the lens holder structure include clip
arms 460 that are aligned to fit into the clip receivers 454 of the
package structure. As described above, matching the clip arms to
the clip receivers causes the imaging optics to be aligned with the
image sensor. In the embodiment of FIGS. 4A 4C, the alignment
features also serve as attachment features. That is, the clip arms
of the lens holder structure help cause the optics system to be
aligned and attached to the package structure.
Because of the high temperatures required for surface mounting
components to circuit boards, in an embodiment, the image sensor
package 416 is soldered to the circuit board 404 without the optics
system 408. In an embodiment, the transparent cover 414 over the
image sensor 410 is protected during surface mounting by a
temporary protective barrier. The temporary protective barrier,
which may be attached to the package structure by the package
structure attachment features, is removed from the transparent
cover before the optics system is attached to the package
structure.
The optics system is attached to the image sensor package after the
image sensor package has been soldered to the circuit board, thus
preventing the imaging optics 420 from being subjected to
potentially damaging high temperatures. In the embodiment of FIGS.
4A 4C, the optics system is clipped directly to the package
structure after the image sensor package has been surface mounted
to the circuit board. The clip arms 460 of the lens holder
structure 418 and the clip receivers 456 of the package structure
402 cause the image sensor 410 to be accurately aligned with
imaging optics when the clip arms are fit into the clip receivers.
Because the optics system is connected directly to the image sensor
package, the optics system does not expand the footprint of the
image sensor package.
In an embodiment of the image capture system, the package structure
includes at least three alignment features that are complementary
to at least three alignment features of the lens holder structure.
In an embodiment of the image capture system, the package structure
includes at least one attachment feature that is complementary to
at least one attachment feature of the lens holder structure.
Preferably, the image sensor package and optics system are
assembled utilizing materials and processes that exclude dust and
moisture from damaging the image sensor and the imaging optics.
In an embodiment, the image sensor package and optics system are
assembled to eliminate air gaps between the internal elements of
the image sensor package or between the rear lens element of the
optics system and the transparent cover of the image sensor
package. In an embodiment, an index matching fluid is placed
between the rear lens element of the optics system and the
transparent cover of the image sensor package to prevent
reflections or other image aberrations.
* * * * *